KI-rrRdCKICSSlVE 'IISSUK CIIANCKS. 223 



URATIC IXFIL'i-RA'noN. 



GENERAL DISCI 'SSIOX 



DEEIA'ITIOX. 



ETfOLOG)' — I h-fiiiciit uric acid secretion. 



APPEARAKCli. 



Macroscopic. 



Microscopic — iXccdIc like crvstuts. 

 TISSUE AFFECTED—Arlicnla'tioiis. 

 EFFECTS. 



Uric acid is formed by the kidneys from urea and passes out 

 normally with the urine. If not prumptlv elinunated, it com- 

 bines with sodium carbonate of the blnod to form sudium urate 

 (quadriurate and biurate). The (piadriurates are unstable but 

 the biurates are quite stable. Uric acid and urates do not nor- 

 mally exist as such in the blood of birds or mammals. The urin- 

 ary excrement of birds is composed of urates but no urea. In 

 liirds the ureter terminates in the cloacum ; the kidney excretion, 

 which is almc)St solid in consistency, is thus mixed with the feces 

 before it is eliminated from the bod}-. This anatomic arrang-e- 

 ment probably fa\-ors the resorption of uric acid. At any rate 

 uratic infiltration is more common in l)irds than in any other 

 domestic animal. 



Sodium urate is the usual compound found in uratic infiltra- 

 tions and when examined miscroscopically appears as a feltwnrk 

 of radiating clusters of needle like cr)-stals. If urate of sodium be 

 treated with a few dr(-)ps of nitric acid, and then e\'aporated to 

 dryness, and to the amorphous residue a few drops of ammo- 

 nium hvdrate be applied, the entire mass assumes a purple-red 

 color, or if potassium h^■droxide be applied, the mass becomes 

 bluish-purple. 



Etiology. — Uratic infiltration is due to deficient excretion 

 of uric acid bv the kidnevs. It may be caused by ligation of the 

 ureters or by any obstruction to these ducts. .\n exclusiye 

 meat or other nitrog'enous diet, sometimes produces uratic infil- 

 tration in fowls. Old age is a predisposing factor. 



Appearance. — Macrosco[>ic. — The jihalangeal, metatarsal and 

 tarsal joints are most frequently affected in fowls. In the begin- 

 ning the condition is e\'idenced by a soft, painful, difTuse SAvell- 

 ing becoming more circumscribed as it becomes larger. The skin 

 o\'er the affected area becomes thickened and scales off as the 

 swelling increases in size. The nodular swellings ultimately 

 rupture, the contents being bufl:' colored and crumbling as it is 

 discharged. Sometimes masses of the urates accumulate as 

 small stones (tophi) under tendons, etc. The articular surfaces 

 are frequently eroded. 



